Lassen Volcano National Park – A Brief History

Lassen Volcano, commonly called Lassen Peak, is California’s most southerly active volcano, located in the Shasta Canyon region of Northern California. It is a portion of the extinct Shasta-Kooz Mountain Range, which was erased during the past Ice Age. The mountain is a portion of the National Park System. Lassen is one of fourteen volcanoes that make up the Shasta-Kooz Mountainrange, a portion of which is within the boundaries of Corns Gorge National Monument.

On April 18, 2021, a swarm of small earthquakes occurred beneath the volcano, which generated ash and smoke into the air. This event was followed by an eruption that lasted approximately two weeks. Since erupting, Lassen has shown signs of progress, with lava flows and small earthquakes being evident. Scientists are monitoring the volcano to learn more about how it erupts and whether or not it will reach a dangerous level.

Scientists know that Lassen does not possess a surface feature like the cone-shaped lavas which are characteristic of typical modern active volcanoes. In addition, there is no evidence of melt water associated with erupting volcanoes, so scientists do not know whether or not the ash from a previous eruption did dissolve into the surrounding atmosphere, making it suitable for breathing. Volcanoes which remain in use often display lava flows, but they do not typically appear to contain any volatile material, as is typical for most other types of volcanic environments. There is some possibility that Lassen may contain materials that have been released by a volcano eruption long ago, but the extent of this remains unknown.

Scientists have conducted several scientific investigations at the Lassen volcano, most notably the study of basal reflectivity and the composition of its lava. The latter revealed that the lava had a very high alkalinity – around 10 times higher than the alkalinity of seawater, which is typical for most volcanic environments. In addition, there are many feldspars within the interior of this lava, which are indicative of metamorphosed rock layers which existed at different times within the past. These layers can help us to better understand the environment of this volcano and how it evolved. During this study, scientists discovered that the majority of this volcano’s surface is made up of fractured rhyolitic units, together with other fine clay particles.

There are a number of interesting implications of this research, one of which is that the volcano’s central rim has a deposit of rhyolite which is roughly the same age as the eruption of the last lava flow, while also containing silica. It is possible that this is another component of the magma, but the fact that it is deposited on the outer rim of the crater lends some credence to the idea that it came from the mantle. Silica is a common mineral of volcanic tuffs and is usually formed in the later stages of eruptions. Although it cannot be seen in the optical spectrum, it is found in many common volcanic rocks, including the Porphyritic dacite, a fine clay material which is formed from gypsum and dolomite when metamorphosed.

This discovery came about through a collaboration between scientists led by Dr. Michael Roth from the University of California at Santa Barbara and Professor Alexander Gerdes from Germany’s University of Tubingen. The two collaborated to examine a series of photographic images taken by a remotely operated vehicle during a period of March and April of this year. Among these images, two showed what is probably the oldest lava flows, dated at 21 years and older, and which formed nearly four hundred years ago. The team is now hoping to get permission to access the area for further research in order to find out more about the eruption and the conditions which led to it. One of the greatest implications is that this earthquake was not just an ordinary event, but the first since Lassen last erupted in 1911.